The present invention relates to the testing of liquid specimens such as urine and the like.
In general, examination of a liquid such as urine is carried out with the use of color reaction test papers. At the present time test methods utilizing color reaction test papers are highly qualitative. Thus, in the strict sense, the known methods and devices will give an indication only as to whether or not the suspected constituent or substance is present or not present in the liquid such as urine. The primary reason for utilizing color reaction test paper so frequently, from among the various types of analyzing means which are available, is, in addition to its simplicity, the fact that the primary object of examining a liquid such as urine is to detect the presence or absence of abnormal substances such as glucose, protein, ect. which normally will not be encountered in the urine of a healthy individual. Clinically, the desired objective is almost entirely achieved simply by judging whether or not such substances are present or absent in the urin or other liquid which is tested.
This reason, however, is in itself not sufficient for entirely supporting the present conditions of use of color reaction papers. Many urine samples which have been judged to give a positive or quasi-positive result after examination require further quantitative examination. Thus, these samples are further examined by quantitative analyzing means such as colorimetric analysis. For this reason it is a well known fact that clinical physicians are not satisfied only with the result of color reaction test paper examination.
In addition, many specialists are doubtful of the ability of color reaction test paper to give a proper indication of the presence or absence of abnormal substances. Thus, it is well known that the capability of achieving a purely qualitative result is unreliable.
In this connection the following example may be considered:
It is well known that a pronounced coloring of the urine itself due to consumption of vitamin compounds by the individual or due to presence of bilirubin will cause errors in measurement. Due to the coloring of the urine itself from such causes, which are given only by way of example, as well as various other causes, it sometimes happens that the individual judging the test paper overlooks slight coloring of the color reaction test paper or believes that a detection has been made of a given substance by way of the color reaction test paper whereas actually the substance is not present and a false judgment has been made. Thus, with conventional color reaction test papers, the individual examining the test paper cannot always correctly judge the presence or absence of abnormal substances and there is a considerable possibility of erroneous judgment. Such erroneous judgment due to overlapping or confusion of the color of the urine itself and the color reaction represents a serious technical drawback which is inevitable when utilizing color reaction test paper.
In order to achieve an accurate measurement it is necessary to use, instead of the unaided eye type of observation, spectral reflection measurement, with high-quality optical instruments being provided for this purpose. With methods of this type also, however, it is difficult to obtain entirely satisfactory results inasmuch as the spectral reflectivity of the color reaction test paper is observed under conditions where there is still an overlap or confusion between the color reaction due to reaction of the reagent in the test paper with the abnormal substance and due to coloring resulting from the colored constituents of the urine itself, as distinct from the substance the presence of which in the urine is to be tested.